ER transmembrane transport Flashcards
Signal recognition proteins do what?
Can they sometimes require GTPase?
These bind to the amino signal sequence and lock up the ribosome.
Yes.
SRP binds to what in the ER membrane?
Signal recognition protein receptor.
What does the signal peptidase enzyme do?
It cuts of the amino signal sequence (used to find ER).
SRP bound to SRP receptor finds what in the membrane?
A protein translocation channel, with 4 sec 61.
How does the sec 61 protein translocation channel stay plugged?
It uses a small alpha helix which opens when it recognizes the signal sequence.
Talk about iodine and dye.
Dye was added to amino acids during synthesis. Iodine was added outside on one sample, and inside on the other. Iodine quenches the dye. This could only happen when the dye was in the lumen of the ER. Showing the poor is water filled and that the compartment seals tight. All a continuous channel.
How many proteins are in Sec61?
3 proteins.
The translocator complex has how many Sec61’s?
4 sec61.
What is co-translational translocation? Who can do it?
It is when translation of mRNA coincides with movement of protein into ER. Archaea, prokaryotes, and eukaryotes.
What is post-translational translocation? Who can do it?
Protein is translocated, post translocation… Eukaryotes and prokaryotes.
How do eukaryotes perform co-translational translocation?
They have a multi section complex (62,63,71,72), which leads protein in. BiP, which is a chaperone protein then binds uses ATP to unbind, and keeps pulling it in not letting it slide back. (kind of pull it through)
How do prokaryotes perform co-translational translocation?
They use SecA. Which uses ATP to push the protein through, it is thought to use a thermal ratchet.
